a common form is where the blade expands around the holdfast and appears pleated or resembles a rosette or a little cabbage

individuals are usually about 5–10 cm tall

Porphyra species have complex life histories. The blade that you see on the shore is just a part of the life history. There is a separate, microscopic phase that lives in shells and is called the conchocelis phase. Look for pink patches on shells because these might be evidence of conchocelis.

ConservationPorphyra umbilicalis is a common species and does not appear to be threatened. However, because part of its life history is hidden in the shells of animals, we should not be complacent. We know very little about the tolerance of the conchocelis phase and do not know how it will respond to influences such as climate change and ocean acidification.